dm-crypt: Extend state buffer size in crypt_iv_lmk_one

dm-crypt: Extend state buffer size in crypt_iv_lmk_one

Add a macro CRYPTO_MD5_STATESIZE for the Crypto API export state
size of md5 and use that in dm-crypt instead of relying on the
size of struct md5_state (the latter is currently undergoing a
transition and may shrink).

This commit fixes a crash on 32-bit machines:
Oops: Oops: 0000 [#1] SMP
CPU: 1 UID: 0 PID: 12 Comm: kworker/u16:0 Not tainted 6.16.0-rc2+ #993 PREEMPT(full)
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
Workqueue: kcryptd-254:0-1 kcryptd_crypt [dm_crypt]
EIP: __crypto_shash_export+0xf/0x90
Code: 4a c1 c7 40 20 a0 b4 4a c1 81 cf 0e 00 04 08 89 78 50 e9 2b ff ff ff 8d 74 26 00 55 89 e5 57 56 53 89 c3 89 d6 8b 00 8b 40 14 <8b> 50 fc f6 40 13 01 74 04 4a 2b 50 14 85 c9 74 10 89 f2 89 d8 ff
EAX: 303a3435 EBX: c3007c90 ECX: 00000000 EDX: c3007c38
ESI: c3007c38 EDI: c3007c90 EBP: c3007bfc ESP: c3007bf0
DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010216
CR0: 80050033 CR2: 303a3431 CR3: 04fbe000 CR4: 00350e90
Call Trace:
 crypto_shash_export+0x65/0xc0
 crypt_iv_lmk_one+0x106/0x1a0 [dm_crypt]

Fixes: efd62c85525e ("crypto: md5-generic - Use API partial block handling")
Reported-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Milan Broz <gmazyland@gmail.com>
Closes: https://lore.kernel.org/linux-crypto/f1625ddc-e82e-4b77-80c2-dc8e45b54848@gmail.com/T/
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>